Effect of Low Night Temperature Treatment on Sucrose Synthesis Ability of Tomato Leaves in Seedling Stage

[Objective] The aim was to explore the effects of low night temperature treatment on sucrose synthesis ability of tomato leaves in seedling stage.[Method] Effects of low night temperature of 6 ℃（with 15 ℃ as control）on the sucrose synthesis ability of tomato leaves were studied after 1,3,5,7 d of treatment.[Result] The contents of fructose,glucose and sucrose in tomato leaves were higher than control at 6：00 during the treatment of low night temperature,but in contrast at 11：00.The contents of fructose,glucose and sucrose in tomato leaves of low night temperature treatment and control group at 6：00 were lower than that at 11：00.The content of starch in tomato leaves was higher than control at 6：00 and 11：00 during the treatment.And the activities of sugar metabolism enzymes of tomato were changed by the treatment of low night temperature.The activities of acid invertase（AI）and neutral invertase（NI）were higher than those of control,while the activities of sucrose synthase（SS）and sucrose phosphate synthase（SPS）were lower than control at 6：00 and 11：00 during the treatment.The activity of all the enzymes at 11：00 of low night temperature treatment plants treated for 1,3,5,7 d was higher than that at 6：00.Compared to 6：00,the invertase activity of the control plant decreased,while the synthetase activity increased.The activity of sucrose synthase（SS）was decreased for treated plants,and the increase amount of sucrose content in leaves was lower than that of control at 11：00 during the treatment,indicating that the sucrose synthesis ability of tomato leaves was decreased by the treatment of low night temperature.[Conclusion] The results in this study had provided theoretical basis for the environmental control of high-yield cultivation of tomato.

Effects on Sucrose Metabolism,Dry Matter Distribution and Fruit Quality of Tomato Under Water Deficit

Four irrigation treatments were designed with 2,4,6 and 8 d intervals to irrigate, respectively. Watering was stopped when the reading of the moisture tension sensor reached zero. The results indicated that glucose and fructose content of tomato's fruit were increased but sucrose content was decreased with fruit growth and development. In different stages, carbohydrate content of tomato fruit in the treatment 3 was the highest, in the treatment 2 was higher, and in the other treatments was the lowest. SS(sucrose synthase)activity was decreased but SPS(sucrose phosphate synthase)activity was increased with development of tomato. SS and SPS activity were increased but acid invertase and neutral invertase activity of ripe stage were decreased under deficit irrigation. Glucose and fructose content were increased in leaves of tomato under water deficit. Soluble sugars, organic acid and the ratio of sugar/acid in tomato fruits were increased and dry matter accumulation of plant was enhanced under water deficit. But the growth of fruits upside the plant and its dry matter accumulation were badly affected under water stress.

Effects of Increased Night Temperature on Cellulose Synthesis and the Activity of Sucrose Metabolism Enzymes in Cotton Fiber

Temperature is one of the key factors that influence cotton fiber synthesis at the late growth stage of cotton. In this paper, using two early-maturing cotton varieties as experimental materials, night temperature increase was stimulated in the field using far-infrared quartz tubes set in semi-mobile incubators and compared with the normal night temperatures （control） in order to investigate the effects of night temperature on the cotton fiber cellulose synthesis during secondary wall thickening. The results showed that the activity of sucrose synthase （SuSy） and sucrose phosphate synthase （SPS） quickly increased and remained constant during the development of cotton fiber, while the activity of acid invertase （AI） and alkaline invertase （NI） decreased, increased night temperatures prompted the rapid transformation of sugar, and all the available sucrose fully converted into cellulose. With night temperature increasing treatment, an increase in SuSy activity and concentration of sucrose indicate more sucrose converted into UDPG （uridin diphosphate-glucose） during the early and late stages of cotton fiber development. Furthermore, SPS activity and the increased concentration of fructose accelerated fructose degradation and reduced the inhibition of fructose to SuSy; maintaining higher value of allocation proportion of invertase and sucrose during the early development stages of cotton fiber, which was propitious to supply a greater carbon source and energy for cellulose synthesis. Therefore, the minimum temperature in the nightime was a major factor correlated with the activity of sucrose metabolism enzymes in cotton fiber. Consequently, soluble sugar transformation and cellulose accumulation were closely associated with the minimum night temperature.

Tomato Key Sucrose Metabolizing Enzyme Activities and Gene Expression Under NaCl and PEG Iso-Osmotic Stresses

Changes in sucrose metabolism in response to salt （NaC1） and water （polyethylene glycol, PEG6000） iso-osmotic stresses were measured in tomato cultivar Liaoyuan Duoli （Solanum lycopersicum L.） and the objective was to provide a new evidence for the relationship between salt and osmotic stresses. The carbohydrate contents, as well as sucrose metabolizing enzymes activities and transcript levels were determined. The results indicated that soluble sugar and hexoses accumulated to higher levels and the contents of sucrose and starch were lower in mature fruit under the two stress treatments. Salt and water stresses can enhance the invertase and sucrose synthase activities of tomato fruit in a long period of time （45-60 days after anthesis）, and elevate the expression of soluble acid invertase mRNA. It showed that two different stresses could also regulate the soluble acid invertase activity by controlling its gene expression. The activity of sucrose synthase was linked to the changes in soluble sugar levels but not with transcript levels. The effects of salt and water stress treatments on sucrose phosphate synthase activities were weak.

Effects of Salt-Alkaline Stress on Carbohydrate Metabolism in Rice Seedlings

The aim of this study was to investigate carbohydrate metabolism in rice seedlings subjected to salt-alkaline stress.Two relatively salt-alkaline tolerant(Changbai 9)and sensitive(Jinongda 138)rice cultivars,grown hydroponically,were subjected to salt-alkaline stress via 50 mM of salt-alkaline solution.The carbohydrate content and the activities of metabolism-related enzymes in the leaves and roots were investigated.The results showed that the contents of sucrose,fructose,and glucose in the leaves and roots increased under salt-alkaline stress.Starch content increased in the leaves but decreased in the roots under salt-alkaline stress.The activities of sucrose-phosphate synthase,sucrose synthase,amylase,and ADP-glucose pyrophosphorylase increased whereas the activities of neutral invertase and acid invertase decreased in the leaves under salt-alkaline stress.The activities of sucrose-phosphate synthase,sucrose synthase,amylase,neutral invertase,and acid invertase increased in the roots under salt-alkaline stress.In conclusion,salt-alkaline stress caused the accumulation of photosynthetic assimilates in the leaves and decreased assimilation export to the roots.

Diet drives convergent evolution of gut microbiomes in bamboo-eating species

Gut microbiota plays a critical role in host physiology and health.The coevolution between the host and its gut microbes facilitates animal adaptation to its specific ecological niche.Multiple factors such as host diet and phylogeny modulate the structure and function of gut microbiota.However,the relative contribution of each factor in shaping the structure of gut microbiota remains unclear.The giant(Ailuropoda melanoleuca)and red(Ailurus styani)pandas belong to different families of order Carnivora.They have evolved as obligate bamboo-feeders and can be used as a model system for studying the gut microbiome convergent evolution.Here,we compare the structure and function of gut microbiota of the two pandas with their carnivorous relatives using 16S rRNA and metagenome sequencing.We found that both panda species share more similarities in their gut microbiota structure with each other than each species shares with its carnivorous relatives.This indicates that the specialized herbivorous diet rather than host phylogeny is the dominant driver of gut microbiome convergence within Arctoidea.Metagenomic analysis revealed that the symbiotic gut microbiota of both pandas possesses a high level of starch and sucrose metabolism and vitamin B12 biosynthesis.These findings suggest a diet-driven convergence of gut microbiomes and provide new insight into host-microbiota coevolution of these endangered species.

Effects of Elevated CO_2 on Growth, Carbon Assimilation, Photosynthate Accumulation and Related Enzymes in Rice Leaves during Sink-Source Transition

To study the effects of growing rice （Oryza sativa L.） leaves under the treatment of the short-term elevated CO2 during the period of sink-source transition, several physiological processes such as dynamic changes in photosynthesis, photosynthate accumulation, enzyme activities （sucrose phosphate synthase （SPS）, and sucrose synthase （SS））, and their specific gene （spsl and RSusl） expressions in both mature and developing leaf were measured. Rice seedlings with fully expanded sixth leaf （marked as the source leaf, L6） were kept in elevated （700 μmol/mol） and ambient （350 mol/L） CO2 until the 7th leaf （marked as the sink leaf, L7） fully expanded. The results demonstrated that elevated CO2 significantly increased the rate of leaf elongation and biomass accumulation of L7 during the treatment without affecting the growth of L6. However, in both developing and mature leaves, net photosynthetic assimilation rate （A）, all kinds of photosynthate contents such as starch, sucrose and hexose, activities of SPS and SS and transcript levels of spsl and RSusl were significantly increased under elevated CO2 condition. Results suggested that the elevated CO2 had facilitated photosynthate assimilation, and increased photosynthate supplies from the source leaf to the sink leaf, which accelerated the growth and sink-source transition in new developing sink leaves. The mechanisms of SPS regulation by the elevated CO2 was also discussed.

Activity, but not Expression, of Soluble and Cell Wall-Bound Acid Invertases Is Induced by Abscisic Acid in Developing Apple Fruit

The present experiment, involving both the in vivo injection of abscislc acid （ABA） Into apple （Malus domestica Brohk.） fruits and the in vivo Incubation of fruit tissues in ABA-contalnlng medium, revealed that ABA activates both soluble and cell wall-bound acid invertases. Immunoblottlng and enzyme-linked Immunosorbent assays showed that this ABA-induced acid invertase activation is Independent of the amount of enzyme present. The acid Invertase activation induced by ABA is dependent on medium pH, time course, ABA dose, living tissue and developmental stage. Two isomers of cls-（＋）-ABA, （-）-ABA and trans- ABA, had no effect on acid invertases, showing that ABA-induced acid invertase activation is specific to physiologically active cis-（＋）ABA. Protein kinase inhlbltors K252a and H7 as well as acid phosphatase Increased the ABA-Induced effects. These data indicate that ABA specifically activates both soluble and cell wall-bound acid Invertases by a posttranslational mechanism probably Involving reversible protein phosphorylatlon, and this may be one of the mechanisms by which ABA Is Involved In regulating fruit development.